Pharmacokinetics

Distribution

TRDağılım
Also known as:Drug distribution

The reversible transfer of a drug from the bloodstream into the interstitial and intracellular fluids and tissues of the body after it has reached the systemic circulation.

In depth

The rate and extent of distribution depend on regional blood flow, capillary permeability, the drug's lipophilicity, ionisation and molecular size, binding to plasma proteins and tissue components, and transport at barriers such as the blood–brain barrier and placenta. Well-perfused organs (brain, heart, liver, kidney) equilibrate first, followed by muscle and, more slowly, adipose tissue.

The extent of distribution is summarised by the apparent volume of distribution (Vd) and its time course by the distribution (α) phase of multi-compartment models. Redistribution from brain to muscle and fat explains the brief action of a single intravenous induction dose of thiopental.

Clinical pearl

Drugs that distribute slowly to their site of action, such as digoxin, should not be sampled for therapeutic drug monitoring until distribution is complete; for digoxin this means at least 6 hours after a dose.

Example drugs

Thiopental Digoxin
TRIn Turkish

Dağılım

Sistemik dolaşıma ulaşan ilacın kandan interstisyel ve hücre içi sıvılara ve vücut dokularına geri dönüşümlü olarak geçmesidir.

Dağılımın hızı ve derecesi; bölgesel kan akımına, kapiller geçirgenliğe, ilacın lipofilisitesi, iyonizasyonu ve molekül büyüklüğüne, plazma proteinleri ve doku bileşenlerine bağlanmasına ve kan–beyin bariyeri ile plasenta gibi engellerdeki taşınmaya bağlıdır. Kanlanması yüksek organlar (beyin, kalp, karaciğer, böbrek) önce dengeye ulaşır; bunları kas ve daha yavaş olarak yağ dokusu izler.

Dağılımın derecesi sanal dağılım hacmiyle (Vd), zaman seyri ise çok kompartmanlı modellerin dağılım (α) fazıyla özetlenir. Beyinden kas ve yağ dokusuna yeniden dağılım, tiyopentalin tek bir intravenöz indüksiyon dozundan sonraki kısa süreli etkisini açıklar.

Etki yerine yavaş dağılan digoksin gibi ilaçlarda terapötik ilaç izlemi için örnek, dağılım tamamlanmadan alınmamalıdır; digoksin için bu, dozdan en az 6 saat sonra anlamına gelir.

Diğer adları:İlaç dağılımı
Updated 24.09.2026 0 views Educational reference — verify against current sources before clinical use.

Read next

Volume of DistributionSanal Dağılım Hacmi

A theoretical volume that describes the extent to which a drug is distributed throughout the body tissues relative to the plasma, indicating how much the drug leaves the bloodstream to enter tissues.

 Plasma Protein BindingPlazma Proteinlerine Bağlanma

The reversible binding of a drug to plasma proteins, chiefly albumin for acidic drugs and α1-acid glycoprotein for basic drugs, which determines the fraction of drug that is free to distribute and act.

 Blood–Brain BarrierKan–Beyin Bariyeri

A selective barrier formed by brain capillary endothelial cells joined by tight junctions and supported by pericytes and astrocyte end-feet, which restricts the passage of drugs and solutes from blood into the central nervous system.

 Compartment ModelKompartman Modeli

A mathematical model that represents the body as one or more kinetically homogeneous, interconnected compartments, used to describe and predict drug concentration–time profiles.

 Unbound FractionSerbest Fraksiyon

The proportion of the total plasma drug concentration that is not bound to plasma proteins, expressed as a fraction (0–1) or percentage; only this free drug can cross membranes and interact with receptors.

 Context-Sensitive Half-TimeBağlama Duyarlı Yarılanma Süresi

The time required for the plasma (central compartment) concentration of a drug to fall by 50% after stopping a continuous infusion of a given duration, the 'context' being the duration of the infusion.